to a novel process for preparing compositions including alkyl(alkyl guloside)uronates or a mixture of alkyl(alkyl guloside)uronates and of alkyl(alkyl mannoside)uronates, exclusively from starting materials which are biobased (alginates, oligoalginates, poly(oligo)guluronates, brown algae) or biocompatible/biodegradable, and also salts and acids thereof.
Some embodiments have for example applications in surfactants, in particular for cosmetics, the phytosanitary field, detergency and CPW (Construction and Public Works).
In the description below, the references between square brackets ([ ]) refer to the reference list presented at the end of the text.
100% biobased surfactants composed of a hydrophilic part and a lipophilic part, both of plant origin, represent approximately 5% to 10% of the total volumes of surfactants. Despite a strong potential in the cosmetics and detergency sectors and in phytosanitary products, they struggle to replace their equivalents of fossil origin. Price difference and a narrower application spectrum explain in particular this difference. The use of starting materials based on algal polysaccharides which are characterized by an original chemical functionality compared with polysaccharides from terrestrial plants, constitutes an approach that could make it possible to broaden the fields of application of the 100% biobased surfactants thus obtained.
Alginates, which are polysaccharides present in the cell wall of brown algae, include or consist of L-guluronic and D-mannuronic acids. While studies have already shown the possibility of exploiting D-mannuronic acid oligomers in the surfactant field, the preparation of compositions based on L-guluronic acid or on mixtures both of L-guluronic acid and of D-mannuronic acid in monomer form and making it possible to exploit all of the saccharides present in the biopolymer, have not been developed to date.
Glycoside surfactants constitute a large family of commercial biobased surfactants. They are surfactants of which the surface properties, the biodegradability and the innocuousness with respect to the skin provide them with many applications in the detergency, cosmetics and food sectors. Sugar-derived non-ionic surfactants are principally represented on the market by alkylpolyglucosides APGs (85 000 t/year), sorbitan esters (20 000 t/year), sucrose esters (<10 000 t/year) and methylglucosides (<10 000 t/year). Sugar-derived anionic surfactants are present on the market to a much smaller extent compared with their nonionic homologs (“Sugar-based Surfactants: fundamentals and applications”, Surfactant science series vol.143, Ed. C. Carnero Ruiz, CRC Press Taylor & Francis Group, 2009 (ISBN 978-1-4200-5166-7)) [1]. This observation can in particular be explained by the difficulty in developing economically viable processes for the controlled introduction of one or more anionic functions onto the saccharide structure. In the carboxylate series, the strategies are based principally on the direct oxidation or esterification of the C6—OH group of alkyl polyglycosides (APGs). An alkyl polyglucoside carboxylate, Plantapon LGC Sorb (INCI name sodium lauryl glucose carboxylate (and) lauryl glucoside) has been introduced onto the market by Cognis as a new anionic surfactant for applications in bodycare formulations. In shampoos and shower gels, it provides a better foaming capacity than the non-ionic surfactants. For bodycare products, it improves the sensory properties. An industrial process based on the reaction of sodium monochloroacetate in an aqueous solution of alkyl polyglycoside (without additional solvent) has been developed in this context (Behler et al., in Proceedings 6th World Surfactant Congress, CESIO June, Berlin, 2004) [2].
Currently, there are not many ways to obtain 100% biobased surfactants in the form of a non-ionic and anionic monomer from one and the same natural source. Surfactants derived from glycosiduronic acids have been produced in the glucu- and galacturonic series in the form of monomers and oligomers (patents EP 0 532 370 and U.S. Pat. No. 5,312,907, patent application FR 2 717 177, international application WO 93/02092) [3-6]. In the guluronic series, surfactants exist in the polymeric form, in particular in the form of modified alginate (international application WO 98/12228, patent U.S. Pat. No. 5,147,861) [7, 8]. Surfactants derived from (Alkyl-D-mannopyranoside)uronic acid have been produced in mono- and dimeric form from D-mannuronic acid oligomers (Benvegnu et al., Topics in Current Chemistry, 294: 143-164, 2010; Roussel et al., Eur. J. Org. Chem., 3085-3094, 2005; patent application FR 02/840306; international application WO 03/104248) [9-12]. The process is based on the production of saturated (acid depolymerization) and unsaturated (enzymatic depolymerization) oligomannuronates which are subsequently converted into monosaccharide and disaccharide intermediates including 2 (monosaccharide) or 4 (disaccharide) butyl chains. These synthons constitute key intermediates in the eco-compatible synthesis (without solvent, without waste, biodegradable reagents) of surfactant structures with a variable hydrophilic-hydrophobic balance, obtained by a process of transesterification/transglycosylation by variable-length fatty alcohols. These surfactants having identical lipophilic chains (two chains in the case of the monosaccharide) can subsequently be saponified in order to obtain anionic surfactants (a single chain in the case of the monosaccharide) including a carboxylic unit. These amphiphilic molecules cover several applications in the detergency and liquid crystal field.
International application WO 03/099870 [13] filed by CEVA relates to the preparation of oligomannuronic and oligoguluronic from fresh or dry algae. This process includes or consists of pre-extraction of the alginates, followed by numerous steps of precipitation by modulating the pH of the reaction medium in order to separate the G blocks and the M blocks constituting the alginates. Finally, an enzymatic or acid hydrolysis step produces the oligomannuronics or oligoguluronics.